JPH06127406A - Power steering device - Google Patents

Abstract

PURPOSE:To reduce vibration of a steering wheel felt by a driver of vehicle as uncomfortable vibration. CONSTITUTION:This power steering device is provided with a steering assist force generation device M1 to generate steering assist force and a steering assist force adjusting device M2 to adjust the steering assist force so as to increase or decrease according to steering torque. Because the steering assist force adjusting device is controlled by means of a steering assist force correcting device M4 according to the vibration level of a steering system detected by means of a vibration detecting device M3, the higher the vibration level of the steering system is, the higher the steering assist force is corrected to be, and the rigidity of the steering system is reduced and hence vibration is hardly transmitted to a steering wheel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering device for vehicles such as automobiles.

[0002]

2. Description of the Related Art Generally, a power steering device for a vehicle such as an automobile increases or decreases the steering assist force according to a steering assist force generating device such as a power cylinder device generating a steering assist force and a steering torque generated on a steering shaft. A steering assist force adjusting device such as a control valve for adjusting is provided, and power assist is performed by generating a required steering assist force according to the steering torque.

As one of such power steering devices, for example, as described in Japanese Patent Application Laid-Open No. 57-74276, a so-called progressive structure configured to reduce the steering assist force as the vehicle speed detected by the vehicle speed sensor increases. Power steering devices are well known in the art. According to such a power steering device, since the steering assist force is generated according to the steering torque and the steering assist force is reduced as the vehicle speed becomes higher, the light steering is ensured in the low vehicle speed range and the medium and high speeds are ensured. Good steering stability in the area is secured.

[0004]

In a steering device for a vehicle such as an automobile, vibration generated in a steering system due to non-uniformity of tires such as flutter is transmitted to a steering wheel through a steering shaft. As a result, the driver of the vehicle may feel uncomfortable vibration of the steering wheel. Such a vibration is likely to occur in a high vehicle speed range, and the vibration is more likely to be transmitted as the rigidity of the steering system is increased by reducing the steering assist force. Accordingly, the case of the progressive power steering device in which the steering assist force is reduced as the vehicle speed increases is more likely to occur than the case of the power steering device which does not change accordingly.

In view of the above-mentioned problems in the conventional power steering apparatus, the present invention provides an improved power steering apparatus capable of reducing the vibration of the steering wheel which is felt as an unpleasant vibration by the driver of the vehicle. It is intended to be provided.

[0006]

According to the present invention, as described above, the above object is to provide a steering assist force generating means M1 for generating a steering assist force, and steering according to a steering torque, as shown in FIG. A power steering device having a steering assist force adjusting means M2 for increasing / decreasing the assist force, and a vibration detecting means M3 for detecting the vibration of the steering system.
And a steering assist force correcting means M4 for controlling the steering assist force adjusting means so that the steering assist force increases as the detected vibration level increases.

[0007]

According to the above configuration, the steering assist force adjusting means is controlled by the steering assist force correcting means M4 in accordance with the level of the vibration of the steering system detected by the vibration detecting means M3, so that the steering system The higher the level of vibration, the higher the steering assist force is corrected, the rigidity of the steering system is reduced, and the vibration of the steering system is less likely to be transmitted to the steering wheel. Vibration is reliably reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments with reference to the accompanying drawings.

FIG. 2 is a schematic configuration diagram showing one embodiment of a power steering apparatus according to the present invention configured as a hydraulic progressive power steering apparatus.

In FIG. 2, 10 is a rack bar which is not shown but is connected to the knuckle arms of the left and right wheels via tie rods at both ends, and 12 is a reciprocating motion of the rack bar 10. Figure 7 shows a housing that supports possible. The rack teeth of the rack bar 10 mesh with a pinion 18 which is rotationally driven by a steering wheel 16 via a steering shaft 14, so that the rack bar 10 can be seen in FIG. 2 by the pinion 18 depending on the direction of rotation of the steering wheel. It is designed to be driven laterally.

In the illustrated embodiment, a power cylinder device 20 as a steering assist force generating means is provided integrally with the housing 12. The power cylinder device 20 includes a cylinder 22 that supports the rack bar 10 so that the rack bar 10 can reciprocate, and a piston 24 that is integrally formed with the rack bar.
The cylinder 22 and the piston 24 cooperate with each other to define a cylinder right chamber 26 and a cylinder left chamber 28. The cylinder right chamber 26 and the cylinder left chamber 28 are respectively provided with conduits 30.
And 32 by the steering shaft 14 and the pinion 1
8 is connected to a control valve 34 as a steering assist force adjusting means. The control valve 34 is connected to a reservoir 42 for storing oil by an oil supply conduit 38 and an oil discharge conduit 40 having an oil pump 36 in the middle.

The control valve 34 is the rack bar 10.
Is driven rightward in the figure by the pinion 18, the oil supply conduit 38 and the conduit 32 are connected to each other to supply high-pressure oil to the cylinder left chamber 28, and the oil discharge conduit 40 and the conduit 30 are connected. Cylinder right chamber 26
The oil inside is discharged to the reservoir 42, and conversely the rack bar 1
When 0 is driven to the left in the figure by the pinion 18, the oil supply conduit 38 and the conduit 30 are connected to each other to supply high-pressure oil to the right chamber 26 of the cylinder, and the oil discharge conduit 40 and the conduit 32. Cylinder left chamber 2
8 is discharged to the reservoir 42, and the degree of communication between the conduits is increased or decreased according to the steering torque generated in the steering shaft 14, so that the power cylinder device 20 generates the oil according to the rotating direction of the steering wheel. The steering assist force is adjusted according to the steering torque.

In the illustrated embodiment, the cylinder right chamber 26
The cylinder left chamber 28 and the cylinder left chamber 28 are connected to each other through a bypass passage 44, and a solenoid valve 46 for controlling the degree of communication is provided in the middle of the bypass passage 44. The solenoid valve 46 is the steering shaft 1.
The electronic control unit 52 controls the steering torque T detected by the torque sensor 48 provided at the center of the vehicle No. 4 and the vehicle speed V detected by the vehicle speed sensor 50. Particularly in the illustrated embodiment, the solenoid valve 46 is configured such that the valve opening amount decreases as the current value of the control current supplied to the solenoid increases.

Although not shown in FIG. 2, the electronic control unit 52 includes a microcomputer having a general structure, and the microcomputer is a central processing unit (CP).
U), a read only memory (ROM), a random access memory (RAM), and an input / output port device, which are connected to each other by a bidirectional common bus. The ROM stores the control program shown in FIG. 3 and maps corresponding to the graphs shown in FIGS. 4 and 5. Further, the CPU is configured to perform various calculations, and particularly for the vibration of the steering shaft 14 included in the steering torque T detected by the torque sensor 48, the function of the FFT analyzer, that is, the signal in the time domain of the vibration is displayed in the frequency domain. It has a function of converting to a signal, and as shown in FIG. 6, it calculates a peak value Gf of a vibration component of a predetermined frequency or more which a person feels as uncomfortable vibration.

Next, the operation of the power steering apparatus constructed as described above will be described with reference to the flow chart shown in FIG.

First, in step 10, the RAM of the microcomputer is initialized, and then step 20
At step 30, the vehicle speed V detected by the vehicle speed sensor 50 is read, and at step 30, step 80 described later is performed.
In step 20, the base current Iv of the control current I output to the solenoid valve 46 is read as the vehicle speed V.
Is calculated from the map corresponding to the graph shown in FIG.

In step 40, the steering torque T detected by the torque sensor 48 is read, and in step 50, the vibration of the steering shaft 14 included in the steering torque T is subjected to frequency analysis. As shown, the peak value Gf of the vibration component above a predetermined frequency that a person feels as uncomfortable vibration is calculated, and in step 60, the correction current Ia of the control current I is calculated in step 50. It is calculated from the map corresponding to the graph shown in FIG.

In step 70, the control current I and the base current Iv calculated in step 30 are compared with step 60.
At step 80, the control current I is calculated as the sum of the correction current Ia calculated at the solenoid valve 46.
The valve opening amount is controlled by being output to the solenoid of No. 2, and as a result, the steering assist force Ta is controlled so as to gradually decrease as the vehicle speed increases and the peak value Gf of vibration is high. The steering assist force is controlled to increase.

Thus, according to the illustrated embodiment, the steering assist force Ta is not only gradually reduced as the vehicle speed V increases, but also the vibration of the steering shaft 14 included in the steering torque T detected by the torque sensor 48 is suppressed. The correction current Ia is set to be higher as the peak value Gf is higher, so that when the steering system vibrates, the steering assist force is corrected to be higher as the level of the vibration is higher. It is possible to not only ensure light steering and good steering stability during high-speed traveling, but also reliably reduce the vibration of the steering wheel that is felt as an unpleasant vibration by the driver of the vehicle.

According to the illustrated embodiment, the steering assist force Ta is increased and corrected only when the steering shaft or the like vibrates, so that the vehicle speed is equal to or higher than a predetermined value regardless of whether or not the vibration occurs. In comparison with the case where the steering assist force is controlled so as to gradually increase as the vehicle speed increases in the area of, the unpleasant vibration is surely reduced while ensuring good steering stability of the vehicle in the high speed traveling range. can do.

Further, according to the illustrated embodiment, the vibration of the steering shaft 14 is frequency-analyzed, and the steering assist force Ta is increased / decreased based on the peak value Gf of the vibration only in the frequency region above a predetermined frequency which is uncomfortable. Therefore, compared with the case where the steering assist force is controlled to increase or decrease based on the peak value of vibration of all frequencies, unpleasant vibration is surely reduced without impairing the original operation of the power steering device. be able to.

Although the present invention has been described above in detail with reference to specific embodiments, the present invention is not limited to such embodiments, and other various embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art that it is possible.

For example, although the above-described embodiment is constructed as a vehicle speed sensitive power steering device, the power steering device of the present invention may be constructed as an engine speed sensitive power steering device, and also of the present invention. The power steering device may be configured as an electric power steering device in which a steering assist force is generated by a motor.

Further, in the above embodiment, the steering assist force correcting means, that is, the solenoid valve 46 increases or decreases the steering assist force generated by the steering assist force generating means, that is, the power cylinder device 20. However, the steering assist force correcting means does not directly increase or decrease the steering assist force, but generates a force in the direction opposite to the direction of the steering assist force or responds to the movement of the steering wheel. The steering assist force may be indirectly increased / decreased by giving frictional resistance.

Further, in the above-mentioned embodiment, the vibration detecting means, that is, the torque sensor 48 is the steering shaft 14.
The vibration of the steering system is detected by detecting the steering torque generated in the steering system. The vibration detecting means detects the vibration of the steering system like an acceleration sensor that detects the reciprocating direction acceleration of the rack bar. It may have any configuration as long as it is possible.

[0026]

As is apparent from the above description, according to the present invention, the steering assist force correcting means M4 is so arranged that the steering assist force becomes higher as the level of the vibration of the steering system detected by the vibration detecting means M3 becomes higher. Since the steering assist force is corrected by the steering system, the higher the level of the vibration of the steering system, the more the rigidity of the steering system is reduced and the vibration is less likely to be transmitted to the steering wheel. Vibration of the wheel can be reliably reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the configuration of a power steering device according to the present invention in correspondence with the description of the claims.

FIG. 2 is a schematic configuration diagram showing one embodiment of a power steering device according to the present invention configured as a hydraulic progressive power steering device.

FIG. 3 is a flowchart showing a control flow achieved by the electronic control device shown in FIG.

FIG. 4 is a graph showing the relationship between vehicle speed V and base current Iv.

FIG. 5 is a graph showing a relationship between a vibration peak value Gf and a correction current Ia.

FIG. 6 is a graph showing an example of frequency analysis of vibration of a steering shaft.

FIG. 7 is a graph showing a relationship between a vehicle speed V and a steering assist force Ta.

[Explanation of symbols]

 10 ... Rack bar 14 ... Steering shaft 16 ... Steering wheel 20 ... Power cylinder device 34 ... Control valve 36 ... Oil pump 44 ... Bypass passage 46 ... Solenoid valve 48 ... Torque sensor 50 ... Vehicle speed sensor 52 ... Electronic control device

Claims (1)

[Claims] 1. A power steering apparatus having steering assist force generating means for generating steering assist force and steering assist force adjusting means for increasing / decreasing the steering assist force according to a steering torque to detect a vibration of a steering system. And a steering assist force correcting unit that controls the steering assist force adjusting unit so that the steering assist force increases as the detected vibration level increases.